Vitellogenesis

Definition

The physiological process by which yolk proteins are synthesized, transported, and deposited in developing oocytes to provision the embryo with metabolic reserves. In arthropods, vitellogenin precursors are typically produced by the fat body (analogous to vertebrate liver), secreted into the hemolymph, and selectively sequestered by oocytes via receptor-mediated endocytosis, forming yolk platelets rich in lipids, phosphoproteins, and carbohydrates. This process is hormonally regulated, often by juvenile hormone in insects and ecdysteroids in some groups, and marks the transition from previtellogenic to vitellogenic oocyte growth.

Etymology

From Latin vitellus (yolk) + Greek -genesis (origin, production)

Example

In the mosquito Aedes aegypti, vitellogenesis is triggered by a blood meal, which stimulates juvenile hormone release from the corpora allata; within 24 hours, massive vitellogenin synthesis begins in the fat body, and yolk deposition makes the ovary visibly white and engorged.

Synonyms

• yolk formation
• yolk deposition

Related Terms

• Vitellogenin
• Oogenesis
• Fat body
• Juvenile hormone
• yolk platelet
• previtellogenesis
• endocytosis
• Fecundity

Usage Notes

Distinguish from oogenesis (the complete process of egg formation, which includes vitellogenesis as one phase) and from vitellogenin (the specific precursor protein, not the process itself). In entomology, specialists often specify 'exogenous vitellogenesis' when yolk precursors are synthesized outside the ovary (typical of most insects) versus 'autogenous' or intra-ovarian mechanisms found in some taxa. The term is sometimes used loosely to refer only to yolk accumulation, but strictly encompasses synthesis, transport, and deposition.